Business columnist

Keeping up the fight: John Hancock is in a court battle with his mother, Gina Rinehart. Photo: Frances Andrijich

John Hancock - the son of Australia's richest person, Gina Rinehart - has declared he is seeing through his grandfather's dying wish by fighting his mother for control of the family fortune.

In his first extensive interview, Mr Hancock has said he ''won't give up'' in his public spat with his mother to remove her as trustee of the multibillion-dollar mining fortune.

In a bitter court dispute, Mr Hancock and one of his three sisters - Bianca Rinehart - are applying to remove their mother as trustee of the Hope Margaret Hancock Trust, alleging she acted ''deceitfully'' and with ''gross dishonesty'' in her dealings. The trial is set for October 1.

Hancock family photos

A selection of private and rare archival images from the Hancock family who are in bitter dispute over the estate of mining magnate Lang Hancock. Photo: Supplied

The trust was set up in 1988 by her father, Lang Hancock, with her children as the beneficiaries.

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''From the start I've said we are doing this to carry out the intentions of my grandfather, and for fairness to everyone,'' John Hancock said. He said that in 1992 he travelled from the US to Perth to visit Lang Hancock on his deathbed. ''He told me, you've got to be strong as you will need to run everything one day.''

The family trust, which controls almost 25 per cent of the family iron ore fortune, was set up to pay for the ''education, advancement and benefit'' of his grandchildren. It was due to vest on September 6, 2011, when the youngest turned 25, giving them financial independence.

Days before, Mrs Rinehart warned her children they would face a capital gains tax bill that would bankrupt them if the trust was allowed to vest.

Mr Hancock later received a binding ruling from the Tax Office that said no capital gains tax was payable. "We want to see our grandfather's wishes honoured,'' Mr Hancock said.

''He [Lang] did not want Gina to have everything or for her to dictate our lives. My grandfather would be greatly troubled. He did not want his discoveries and life's work to be a source of problems, but rather a great start and foundation for us, his grandchildren.

''He'd be furious Hancock Prospecting staff have involved themselves with these matters, and so am I, quite frankly."

This week Mrs Rinehart attempted to stop the trial and send the matter to arbitration. It comes days after Mr Hancock was given access to hundreds of pages of documents between Hancock Prospecting chief financial officer Jay Newby and PricewaterhouseCoopers, which provided advice that was relied upon to tell the children capital gains tax would bankrupt them.

"My hope is my mother is just doing this to apply the blowtorch and see what my melting point is."

Mrs Rinehart believes her children are ''manifestly unsuited'' to running the trust. Documents filed in the court state that none of the plaintiffs has ''the requisite capacity or skill or the knowledge, experience, judgment or responsible work ethic'' to manage it.